Artificial knee-joint

Abstract

The artificial knee joint for an artificial leg includes a pair of substantially parallel pivotable bars which are connected by pivoting joints to an upper part and a lower part of the knee joint, respectively. One of the bars is anterior and the other is posterior with respect to a position of the artificial leg. The upper part has two spaced pivoting joints and the lower part has two spaced pivoting joints. The imaginary connecting line between the pivoting joint of the anterior bar and the pivoting joint of the posterior bar is substantially horizontal when the leg is in its vertical position. The imaginary connecting line between two pivoting joints of the anterior bar is inclined at a small angle to the imaginary connecting line between two pivoting joints of the posterior bar.

We claim: 
     
       1. An artificial knee joint for an artificial leg, comprising an upper joint part including an anterior pivoting joint and a posterior pivoting joint spaced from each other; a lower joint part also including an anterior pivoting joint and a posterior pivoting joint spaced from one another; a pivotable anterior connecting bar interconnected between the anterior pivoting joint of said upper part and the anterior pivoting joint of said lower part; and a pivotable posterior connecting bar interconnected between the posterior pivoting joint of said upper part and the posterior pivoting joint of said lower part, the imaginary connecting line extending between the anterior pivoting joint of said lower part and the posterior pivoting joint of said lower part being substantially horizontal when the leg is in a vertical position, and the imaginary connecting line extending between the anterior pivoting joint of said upper part and the anterior pivoting joint of said lower part being inclined at a relatively small angle relative to the imaginary connecting line extending between the posterior pivoting joint of said upper part and the posterior pivoting joint of said lower part. 
     
     
       2. The joint of claim 1, wherein the ratio between the distance between the anterior pivoting joint and the posterior pivoting joint of said upper part and the distance between the anterior pivoting joint and the posterior pivoting joint of said lower part and the distance between the posterior pivoting joint of said upper part and the posterior pivoting joint of said lower part is approximately 1:2:4. 
     
     
       3. The joint of claim 1, wherein said anterior connecting bar and said posterior connecting bar are of the identical shape. 
     
     
       4. The joint of claim 3, wherein said connecting bars are inserted into the knee joint substantially at an angle of 180° relative to each other with addition or subtraction of said small angle. 
     
     
       5. The joint of claim 4, wherein the imaginary connecting line extending between the anterior pivoting joint and the posterior pivoting joint of said lower part is substantially perpendicular to the imaginary connecting line extending between the posterior pivoting joint of said upper part and the posterior pivoting joint of said lower part. 
     
     
       6. The joint of claim 5, wherein said connecting bars each has an angular shape. 
     
     
       7. The joint of claim 5, wherein said connecting bars each has a shape of a circular segment. 
     
     
       8. The joint of claim 7, wherein said upper and said lower parts each has two bores spaced from each other and each of said pivoting joints includes a dowel fitted into a respective bore of said lower and upper joint parts. 
     
     
       9. The joint of claim 8, wherein each of said dowels is hollow. 
     
     
       10. The joint of claim 9, wherein each of said pivoting joints further includes a pin connected to a respective bar and insertable into a respective dowel. 
     
     
       11. The joint of claim 10, further including a locking element interconnected between the dowels of the anterior pivoting joint and the posterior pivoting joint of said lower joint part. 
     
     
       12. The joint of claim 11, wherein the pin insertable into the dowel of the anterior pivoting joint is a screw secured on said dowel against rotation. 
     
     
       13. The joint of claim 12, further including a friction brake arranged at one end of said screw. 
     
     
       14. The joint of claim 13, wherein said friction brake includes a plurality of friction discs outwardly extending from the dowel of said anterior pivoting joint of said lower joint part. 
     
     
       15. The joint of claim 14, wherein at least two of said discs are secured on the dowel of said anterior pivoting joint of said lower part against rotation. 
     
     
       16. The joint of claim 15, wherein said friction discs are alternately arranged discs of metal and plastic. 
     
     
       17. The joint of claim 16, further including a spring element clamped between said lower joint part and said posterior connecting bar. 
     
     
       18. The joint of claim 17, wherein said spring element is a helical spring. 
     
     
       19. The joint of claim 18, wherein said spring is pretensioned and wherein means for adjusting the position of said spring between said lower joint part and said posterior connecting bar are provided. 
     
     
       20. The joint of claim 19, wherein said adjusting means includes a bolt supporting said spring and having a thread and a stop pin threadably adjustable along the thread of said bolt and retaining said spring. 
     
     
       21. The joint of claim 20, further including a stop mounted on said lower joint part and operative for delimiting the rearward movement of said anterior connecting bar. 
     
     
       22. The joint of claim 21, wherein said stop is adjustable. 
     
     
       23. The joint of claim 22, wherein said stop has a projection with an external thread, said lower joint part having a threaded bore receiving said projection.